Wireless charging apparatus based on three-dimensional (3d) wireless charging zone

ABSTRACT

Provided is a wireless charging apparatus for performing wireless charging of an electronic device including a receiving coil located in a three-dimensional (3D) wireless charging zone using a plurality of transmitting coils arranged in the 3D wireless charging zone and at least one power source configured to supply a current to the plurality of transmitting coils.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the priority benefit of Korean PatentApplication No. 10-2015-0182693 filed on Dec. 21, 2015 and Korean PatentApplication No. 10-2016-0028366 filed on Mar. 9, 2016 in the KoreanIntellectual Property Office, the disclosures of which are incorporatedherein by reference for all purposes.

BACKGROUND 1. Field

One or more example embodiments relate to a wireless charging apparatususing a three-dimensional charging zone and, more particularly, anapparatus for constructing a wireless charging environment to improve anefficiency of wireless charging performed by an electronic device.

2. Description of Related Art

With increases of users using portable smartphones, the smartphones havebeen developed to provide various functions such as an Internet browser,a camera, and an application to satisfy various desires of the users.

Functions may be provided as various applications for user conveniences.When a user executes the functions in the smartphone, a battery includedin the smartphone may be discharged. Thus, the user may charge thebattery to continuously use the function in the smartphone. In general,the user may use an adapter connected to a charging terminal of thesmartphone to charge the battery. Recently, according to acommercialization of wireless charging technology for charging a batteryin lieu of using an adapter for charging the battery, the user mayconveniently charge the battery without need to use the adapter.

The wireless charging technology may be technology for charging abattery of a smartphone using a transmitting resonator and a receivingresonator included in each of the smartphone and a wireless chargingapparatus. The transmitting resonator and the receiving resonator mayoperate in a wireless a small electronic device such as a smartphone anda wireless charging apparatus. Thus, sizes of the transmitting resonatorand the receiving resonator may be reduced such that the transmittingresonator and the receiving resonator are provided in sufficiently smallsizes.

The reduced sizes of the transmitting resonator and the receivingresonator have allowed the transmitting resonator and the receivingresonator to be readily installed in the smartphone and the wirelesscharging apparatus. However, according to decreases in the sizes oftransmitting resonator and the receiving resonator, a transmissiondistance through which a current flows may also be reduced and thus, thetransmitting resonator and the receiving resonator may be used under acondition of spatial restrictions in practice. When a diameter of areceiving resonator is D, it is difficult to design and manufacture thereceiving resonator that provides a transmission distance of at least80% radio frequency (RF) efficiency at a level corresponding to thediameter of the receiving diameter simultaneously with realize thereceiving resonator in a sufficiently small size. Also, even if it ispossible to develop such resonator, a transmission distance of theresonator may be limited to a diameter of the resonator.

To solve this, magnetic resonance-based wireless charging technology hasbeen suggested. In general, the magnetic resonance-based wirelesscharging technology may have a characteristic of medium-rangetransmission performed in about one meter and a diameter of a resonatormay correspond to a maximum transmission distance. Thus, there has beenan effort to expand the transmission distance.

In addition to the aforementioned issue, a transmission distance limitmay exist in a magnetic resonance method based on a combination ofresonance modes. In view of most of research results, papers, and patentof related arts, a diameter of a resonator may be recognized as a mostpractical transmission distance in general. As another condition, thewireless power transmission may be available in only a predeterminedarea including a transmitting resonator.

Also, despite an equal transmission distance, an efficiency may varybased on a distance between the transmitting resonator and the receivingresonator and the efficiency may be susceptible to a direction. Forexample, when the transmitting resonator and the receiving resonator aredisposed to face each other, the efficiency may be maintained to bemaximized. In contrast, when the receiving resonator is disposed atangle of 45° or 90°, the efficiency may significantly decrease.

Accordingly, there is a desire for a method of efficiently transmittingwireless power based on transmission distance and direction of awireless charging.

SUMMARY

An aspect provides wireless charging and energy transmitting technologyhaving an increased degree of freedom in a three-dimensional (3D) areato expand a range of wireless power transmission in a process ofperforming wireless charging when compared to a pad structurecorresponding to a two-dimensional (2D) area.

Another aspect also provides a structure of resonance coil for realizinga method of transmitting wireless power based on a 3D wireless chargingzone.

According to an aspect, there is provided a wireless charging apparatusincluding a plurality of transmitting coils included in a wirelesscharging zone in a 3D form and at least one power source configured tosupply a current to the plurality of transmitting coils, wherein theplurality of transmitting coils includes at least one pair oftransmitting coils arranged to face each other in the wireless chargingzone.

The at least one pair of transmitting coils may be configured to form aquiet zone in the wireless charging zone using the current supplied fromthe at least one power source.

The at least one pair of transmitting coils may be configured to form aquiet zone in a direction the same as a direction of at least onereceiving coil present in the wireless charging zone.

The direction of the at least one receiving coil may be a direction inwhich an induced current is formed on the receiving coil through acoupling with one of the plurality of transmitting coils included in thewireless charging zone.

The at least one power source may be configured to supply currents tothe at least one pair of transmitting coils such that phases of thecurrents differ by 90 degrees.

The at least one power source may be configured to supply an in-phasecurrent or an out-of-phase current to the plurality of transmittingcoils included in the wireless charging zone.

The wireless charging apparatus may further include at least onecapacitor configured to reduce sizes of the plurality of transmittingcoils or reduce resonant frequencies of the transmitting coils.

The at least one capacitor may be located between the at least one powersource and the plurality of transmitting coils.

The at least one power source may include an inverter configured tocontrol a phase of the current supplied to the plurality of transmittingcoils.

The inverter may be configured to control the phase of the currentsupplied to the plurality of transmitting coils based on gradientsbetween the transmitting coils and a receiving coil present in thewireless charging zone or a location of the receiving coil.

The current may have a difference in phase between the at least one pairof transmitting coils in the wireless charging zone or includes at leasttwo phases having the same phase.

The wireless charging apparatus may further include a communicatorconfigured to detect an induced current formed on the plurality oftransmitting coils in the wireless charging zone.

The inverter may be configured to control a phase of a current initiallyset to be supplied to the plurality of transmitting coils based on theinduced current detected by the communicator.

According to another aspect, there is also provided a wireless chargingapparatus including at least one pair of transmitting coils arranged toface each other in a wireless charging zone in a 3D form, a power sourceincluding an inverter configured to control a phase of a currentsupplied to the at least one pair of transmitting coils, at least onecapacitor configured to reduce sizes of the at least one pair oftransmitting coils or reduce resonant frequencies of the at least onepair of transmitting coils, and a communicator configured to detect aninduced current formed on at least one pair of transmitting coilspresent in the wireless charging zone.

The at least one pair of transmitting coils may be configured to form aquiet zone in the wireless charging zone using the current supplied fromthe power source.

The at least one pair of transmitting coils may be configured to form aquiet zone in a direction the same as a direction of at least onereceiving coil present in the wireless charging zone.

The at least one power source may be configured to supply an in-phasecurrent or an out-of-phase current to the at least one pair oftransmitting coils arranged in the wireless charging zone.

The inverter may be configured to control a phase of a current suppliedto the at least one pair of transmitting coils based on gradientsbetween the at least one pair of transmitting coils and a receiving coilpresent in the wireless charging zone or a location of the receivingcoil.

The current may have a difference in phase between the at least one pairof transmitting coils arranged in the wireless charging zone or includesat least two phases having the same phase.

The inverter may be configured to control a phase of a current initiallyset to be supplied to the at least one pair of transmitting coils basedon the induced current detected by the communicator.

Additional aspects of example embodiments will be set forth in part inthe description which follows and, in part, will be apparent from thedescription, or may be learned by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects, features, and advantages of the inventionwill become apparent and more readily appreciated from the followingdescription of example embodiments, taken in conjunction with theaccompanying drawings of which:

FIG. 1 is a diagram illustrating a wireless charging apparatus using athree-dimensional (3D) wireless charging zone according to an exampleembodiment;

FIGS. 2A through 2C are diagrams illustrating transmitting coilsarranged in a wireless charging zone according to an example embodiment;

FIGS. 3A and 3B are diagrams illustrating transmitting coils and a quitezone formed on the transmitting coils according to an exampleembodiment:

FIG. 4 is a diagram illustrating an example of an operation in which acoupling of a transmitting coil with a receiving coil occurs in awireless charging zone according to an example embodiment;

FIG. 5 is a diagram illustrating another example of an operation inwhich a coupling of a transmitting coil and a receiving coil occurs in awireless charging zone according to an example embodiment:

FIG. 6 is a diagram illustrating a transmitting coil including acapacitor according to an example embodiment;

FIG. 7 is a diagram illustrating an operation of offsetting magneticfield formed on transmission coils arranged in a wireless charging zoneaccording to an example embodiment:

FIG. 8 is a graph illustrating a change in efficiency based on agradient between a receiving coil and a transmitting coil according toan example embodiment;

FIGS. 9A and 9B are diagrams illustrating a change in efficiency of theoffset magnetic field of FIG. 7 according to an example embodiment;

FIG. 10 is a diagram illustrating current characteristics based on achange in phase of a current supplied from a power source according toan example embodiment;

FIGS. 11A and 11B are diagrams illustrating an operation of controllinga phase of a magnetic field formed on transmission coils using aninverter included in a power source according to an example embodiment:

FIGS. 12A through 12E are diagrams illustrating results of evaluation onan efficiency of a wireless charging apparatus using a 3D wirelesscharging zone according to an example embodiment;

FIGS. 13A and 13B are diagrams illustrating a comparison between quitezones formed on transmitting coils arranged in a 3D wireless chargingzone according to an example embodiment;

FIG. 14 is a diagram illustrating magnetic fields formed based on phasesof currents according to an example embodiment; and

FIG. 15 is a flowchart illustrating an operation performed by aprocessor of a wireless charging apparatus according to an exampleembodiment.

DETAILED DESCRIPTION

Hereinafter, some example embodiments will be described in detail withreference to the accompanying drawings. Regarding the reference numeralsassigned to the elements in the drawings, it should be noted that thesame elements will be designated by the same reference numerals,wherever possible, even though they are shown in different drawings.Also, in the description of embodiments, detailed description ofwell-known related structures or functions will be omitted when it isdeemed that such description will cause ambiguous interpretation of thepresent disclosure.

FIG. 1 is a diagram illustrating a wireless charging apparatus using athree-dimensional (3D) wireless charging zone according to an exampleembodiment.

Referring to FIG. 1, a wireless charging apparatus 101 may be located ina 3D wireless charging zone 106 to perform a wireless charging of anelectronic device present in the 3D wireless charging zone 106. Thewireless charging apparatus 101 may include transmitting coils 102, 103,104, and 105 arranged in the 3D wireless charging zone 106 and powersources 108 and 109 configured to supply currents to the transmittingcoils 102, 103, 104, and 105. The wireless charging apparatus 101 mayuse the transmitting coils 102, 103, 104, and 105 and the power sources108 and 109 to form an energy zone for wireless charging based on the 3Dwireless charging zone 106. For example, the wireless charging apparatus101 may form magnetic fields on the transmitting coils 102, 103, 104,and 105 arranged in the 3D wireless charging zone 106. In this example,the 3D wireless charging zone 106 may be an energy zone formed based ona quiet zone of the magnetic fields formed on the transmitting coils102, 103, 104, and 105. The quiet zone may indicate a magnetic fieldhaving an equalized energy density corresponding to each of the magneticfields formed on the transmitting coils 102, 103, 104, and 105. Thequiet zone may indicate a region in which the magnetic fields aredensely formed between the transmitting coils 102, 103, 104, and 105arranged in parallel in the 3D wireless charging zone 106 and an energydensity of the magnetic fields is equalized.

The transmitting coils 102, 103, 104, and 105 may be arranged in variouslocations based on a structure in which the 3D wireless charging zone106 is realized. For example, in terms of a structure in a cylindricalshape or a quadrangular shape, the transmitting coils 102, 103, 104, and105 may be arranged in various locations such as a wall, a ceiling, afloor, and a corner of the structure. Related descriptions will also beprovided with reference to FIGS. 2A and 2B.

Also, the transmitting coils 102, 103, 104, and 105 arranged in the 3Dwireless charging zone 106 may include at least one pair of transmittingcoils arranged to face each other in the 3D wireless charging zone 106.In this example, the transmitting coils 102, 103, 104, and 105 may beprovided as a plurality of pairs of transmitting coils. For example, thewireless charging apparatus 101 may arrange four transmitting coils oneach side of the 3D wireless charging zone 106 provided in a form ofsquare. Each of the four transmitting coils may be paired with acounterpart transmitting coil in the 3D wireless charging zone 106.

In the 3D wireless charging zone 106, at least one pair of transmittingcoil facing each other may form a quite zone and compose a predeterminedenergy density using the formed quite zone, thereby improving anefficiency of an energy generated in a predetermined space.

The transmitting coils 102, 103, 104, and 105 may form the magneticfields using the currents supplied from the power sources 108 and 109.Each of the transmitting coils 102, 103, 104, and 105 may receive thecurrent from the same one or a different one between the power sources108 and 109. For example, when arranging the transmitting coils 102,103, 104, and 105 in the 3D wireless charging zone 106, the wirelesscharging apparatus 101 may arrange two pairs of transmitting coils, apair of the transmitting coils 103 and 105 and a pair of thetransmitting coils 102 and 104.

The pair of the transmitting coils 103 and 105 and the pair of thetransmitting coils 102 and 104 may form a fine quiet zone when thecurrent supplied to the power sources 108 and 109 has phases differingby 90 degrees. Thus, a different in phase between the current suppliedto the transmitting coils 103 and 105 and the current supplied to thetransmitting coils 102 and 104 may be 90 degrees. In this disclosure, acurrent having the same phase may also be referred to as, for example,an in-phase current and a current having different phases may also bereferred to as, for example, an out-of-phase current.

The pair of the transmitting coils 103 and 105 may receive the currentfrom the power source 108 and the pair of transmitting coils 102 and 104may receive the current from the power source 109. The transmittingcoils 102, 103, 104, and 105 may be connected to different power sourcesor the same power source to receive currents. Also, the power sources108 and 109 may transmit a preset current to the transmitting coils 102,103, 104, and 105.

The wireless charging apparatus 101 may detect weather a receiving coil107 is present in the 3D wireless charging zone 106. The wirelesscharging apparatus 101 may recognize an electronic device including thereceiving coil 107 and verify whether the receiving coil 107 is present.For example, the wireless charging apparatus 101 may detect theelectronic device including the receiving coil 107 in the 3D wirelesscharging zone based on a location-based communication technology. Thelocation-based communication technology may include, for example,near-field communication (NFC), Bluetooth, and a wireless fidelity(Wi-Fi).

The wireless charging apparatus 101 may detect an induced current formedon the receiving coil 107 coupled with at least one transmitting coilbased on the receiving coil 107 in the 3D wireless charging zone 106.For example, a coupling with the receiving coil 107 may occur by thequiet zone formed on at least one of the transmitting coils 102, 103,104, and 105 arranged in the 3D wireless charging zone 106, and thewireless charging apparatus 101 may detect the induced current formed onthe receiving coil 107 with which the coupling occurs.

The induced current formed on the receiving coil 107 may be a currentinduced through the coupling with the receiving coil 107 by the quietzone formed on the transmitting coils 102, 103, 104, and 105 based onthe preset current supplied from the power sources 108 and 109. Also,the induced current formed on the receiving coil 107 may have a value ofcurrent varying based on a change in location of the receiving coil 107in the 3D wireless charging zone 106.

The wireless charging apparatus 101 may change the phase of the currentsupplied to the transmitting coils 102, 103, 104, and 105 based on theinduced current of the receiving coil 107 detected to correspond to alocation of the receiving coil 107 in the 3D wireless charging zone 106.For example, the wireless charging apparatus 101 may change a phase of acurrent generated in a power source to a phase of a current previouslyset in the power source to correspond to an induced current between thereceiving coil 107 and the transmitting coils 102, 103, 104, and 105.Also, the power sources 108 and 109 may supply the current having thechanged phase to the transmitting coils 102, 103, 104, and 105.

Thereafter, the wireless charging apparatus 101 may redetect an inducedcurrent formed on the receiving coil 107 by the quite zone formed on thetransmitting coils 102, 103, 104, and 105 based on the current havingthe changed phase. Also, when the redetected induced current is in anormal state, the wireless charging apparatus 101 may maintain a phaseof the induced current and perform charging of the electronic deviceincluding the receiving coil 107. By supplying the current havingdifferent phases based on the location of the receiving coil 107 in the3D wireless charging zone 106 to the transmitting coils 102, 103, 104,and 105 the wireless charging apparatus 101 may perform the chargingwithout restrictions associated with the 3D wireless charging zone 106.Here, the normal state may be a state based on whether an amount ofwireless power for charging a battery of the electronic device includingthe receiving coil 107 is sufficient to charge the battery.

Wireless charging technology using the wireless charging apparatus 101may be applicable to various devices, for example, a pad-type devicesuch as a smartphone, and may exert significant influence on activationsof wearable devices and Internet of things (IoT) devices. Also, thewireless charging technology using the wireless charging apparatus 101may allow automatic charging of small wearable devices which may bedifficult to be charged using a wire and to change a battery while thesmall wearable devices are located in a predetermined space so as toprovide a convenience to a user.

When an electronic device enters in the 3D wireless charging zone 106having X, Y, Z axes, a battery of the electronic device may beautomatically charged through resonances between a receiving coilincluded in the electronic device and transmitting coils arranged on oneof the X, Y, Z axes of the 3D wireless charging zone 106 based on awireless transmission method of a predetermined space.

FIGS. 2A through 2C are diagrams illustrating transmitting coilsarranged in a wireless charging zone according to an example embodiment.

Referring to FIGS. 2A through 2C, transmitting coils may be disposed atvarious locations in a wireless charging zone. The transmitting coilsmay form a quiet zone on the wireless charging zone using a currentsupplied from at least one power source.

Referring to FIG. 2A, the transmitting coils may be disposed on a wall,a ceiling, and a floor of the wireless charging zone. In this example,the transmitting coils may be disposed on a wall and a ceiling to faceone another and also be disposed on walls facing each other.

Referring to FIG. 2B, the transmitting coils may be disposed on fourwalls of the wireless charging zone. In this example, at least onetransmitting coil may be disposed on one wall such that an area of aquiet zone formed around the at least one transmitting coil is expanded.FIG. 2B may be of a concept extended from a configuration of forming aquiet zone using a single transmitting coil. In an example of FIG. 2B, aplurality of transmitting coils may be arranged in consideration of acase in which an area of the wireless charging zone is relatively large,or a relatively strong current is required.

Referring to FIG. 2C, the transmitting coils may be disposed at cornersof the ceiling or corners of the floor in the wireless charging zone. Inthis example, the transmitting coils arranged in the 3D wirelesscharging zone may be arranged in various forms in addition to theaforementioned examples of FIGS. 2A through 2C. In this disclosure, astructure of connecting a pair of transmitting coils in parallel and astructure of connecting a pair of transmitting coils in series may beprovided in an arrangement of the transmitting coils. Also, theresonance may be autonomously performed between the transmitting coilsor an additional cap may be used to perform the resonance between thetransmitting coils.

FIGS. 3A and 3B are diagrams illustrating transmitting coils and a quitezone formed on the transmitting coils according to an exampleembodiment.

FIG. 3A illustrates the transmitting coils 102, 103, 104, and 105included in the 3D wireless charging zone 106. As illustrated in FIG.3A, a wireless charging apparatus may include a plurality oftransmitting coils, for example, the transmitting coils 102, 103, 104,and 105 and at least one power source, for example, the power sources108 and 109.

The transmitting coils 102, 103, 104, and 105 may be arranged in the 3Dwireless charging zone 106. In the 3D wireless charging zone 106, atleast one pair of transmitting coils may be arranged to face each other.Here, an arrangement structure of the 3D wireless charging zone 106 maybe a structure in which the transmitting coils 102, 103, 104, and 105are arranged in each interval corresponding to a predetermined size ofarea in the 3D wireless charging zone 106 such that the transmittingcoils 102, 103, 104, and 105 maintain a predetermined level ofefficiency in each interval of the 3D wireless charging zone 106.

The arrangement structure may be for constantly receiving an inducedcurrent irrespective of a location of a receiving coil when thereceiving coil is present in an area as indicated by a box with a dashedline. For example, the transmitting coils 102, 103, 104, and 105corresponding to the at least one pair of transmitting coils arranged toface each other may form a quite zone in the 3D wireless charging zone106 using a current supplied from the power sources 108 and 109.

In this example, the power sources 108 and 109 may control the currentto flow in the same direction to the at least one pair of transmittingcoils facing each other such that the quiet zone is formed in the 3Dwireless charging zone between the pair of transmitting coils. Inresponse to the controlled current being received by the transmittingcoils 102, 103, 104, and 105, a magnetic field having a predeterminedwavelength may be formed between the transmitting coils arranged as apair.

Through this, in the 3D wireless charging zone 106, a charging area inwhich an energy density is constantly maintained by the quite zoneformed by the transmitting coils 102, 103, 104, and 105 may be provided.In this example, the transmitting coils 102, 103, 104, and 105 may berealized as at least one pair of transmitting coils arranged to faceeach other and a quiet zone may be densely formed between thetransmitting coils realized as a pair. Accordingly, a magnetic fieldhaving an energy density in a more equalized state may be formed.

Thereafter, the receiving coil may be located in the 3D wirelesscharging zone 106 having an equalized energy density and thus, mayreceive an equal induced current from the transmitting coils 102, 103,104, and 105 irrespective of a location of the receiving coil.

In FIG. 3A, a pair of the transmitting coils 102 and 104 mayhorizontally form the quite zone, and a pair of the transmitting coils103 and 105 may vertically form the quite zone. The power source 109connected to the transmitting coils 102 and 104 and the power source 108connected to the transmitting coils 103 and 105 may output an in-phasecurrent. In an example of FIG. 3A, a phase of the current supplied tothe transmitting coils 103 and 105 may be different from a phase of thecurrent supplied to the transmitting coils 102 and 104. In other words,an operation of adjusting an equalized magnetic field in the 3D wirelesscharging zone may be performed to provide a normal charging function tothe receiving coil located in the 3D wireless charging zone. When thetransmitting coils 102, 103, 104, and 105 are arranged on four walls ofthe 3D wireless charging zone, the pair of the transmitting coils 103and 105 may be set to receive the in-phase current and the pair of thetransmitting coils 102 and 104 may be set to receive the out-of-phasecurrent.

The phase of the current supplied to the transmitting coils 103 and 105may be set to be different from the phase of the current supplied to thetransmitting coils 102 and 104 such that a different in phase of 90degrees occurs in the currents supplied to the transmitting coils 102,103, 104, and 105. For example, the phase of the current supplied to thetransmitting coils 103 and 105 may be zero degrees and the phase of thecurrent supplied to the transmitting coils 102 and 104 may be 90degrees. In this example, the phase of the current supplied to thetransmitting coils 103 and 105 may differ from the phase of the currentsupplied to the transmitting coils 102 and 104 by 90 degrees.

Accordingly, a difference between a minimum current value and a maximumcurrent value may be reduced when the transmitting coils 103 and 105 andthe transmitting coils 102 and 104 receive a 90-degree out-of-phasecurrent in comparison to the in-phase current and thus, a density of thequite zone formed in the 3D wireless charging zone may increase.

FIG. 3B illustrates between transmitting coils arranged as a pair, aform of a quite zone formed between the transmitting coils, and alocation based on a connection between the transmitting coils.

A wireless charging apparatus may supply a current flowing in the samedirection to the transmitting coils 105′ and 105″ arranged as a pair.Also, the wireless charging apparatus may allow a quite zone to beformed in an area in which a distribution of a magnetic field isindicated by dotted lines, that is, the 3D wireless charging zone 106 bya current supplied to the transmitting coils 105′ and 105″ arranged asthe pair.

FIG. 3B may be based on a concept extended from an example of FIG. 3A.By arranging a plurality of transmitting coils to be provided as a pairin a predetermined interval of the 3D wireless charging zone 106, thewireless charging apparatus may be implemented in a structure thatincreases the number of pairs of coils such that a quite zone is formedwith respect to a receiving coil receiving a current from thetransmitting coils although a direction of the receiving coil is rotatedby 90 degrees.

FIG. 4 is a diagram illustrating an example of an operation in which acoupling of a transmitting coil with a receiving coil occurs in awireless charging zone according to an example embodiment.

Referring to FIG. 4, in response to a coupling occurring between one ofthe transmitting coils 102, 103, 104, and 105 and the receiving coil 107located in the 3D wireless charging zone 106, a wireless chargingapparatus may form an induced current on the receiving coil 107. In thisexample, the wireless charging apparatus may form the quite zone in adirection the same as a direction of at least one receiving coil, thereceiving coil 107 located in the 3D wireless charging zone 106.

The wireless charging apparatus may determine a direction correspondingto a location of the receiving coil 107 in the 3D wireless charging zone106. The wireless charging apparatus may form a quite zone in adirection the same as the determined direction of the receiving coil107.

For example, the receiving coil 107 may be vertically disposed in the 3Dwireless charging zone 106, and located adjacent to the transmittingcoil 103 among the transmitting coils 102, 103, 104, and 105. In thisexample, the wireless charging apparatus may vertically form the quitezone using the transmitting coils 103 and 105. Since the receiving coil107 is located in a vertical direction in the 3D wireless charging zone106, the receiving coil 107 may be connected to the transmitting coils103 and 105 forming a magnetic field in a vertical axis direction. Thetransmitting coils 103 and 105 may receive most of the current from thepower source 108.

Also, the induced current may be formed on the receiving coil 107through a resonance between the receiving coil 107 and the transmittingcoil 103 having a higher coupling coefficient between the transmittingcoils 103 and 105. In other words, when the receiving coil 107 iscoupled with one of a plurality of transmitting coils, the inducedcurrent may be formed by a transmitting coil located adjacent to thereceiving coil 107. For example, a magnetic field may be formed on thereceiving coil 107 by a quite zone formed on the transmitting coil 103,and an induced current may be formed based on the magnetic field.

FIG. 5 is a diagram illustrating another example of an operation inwhich a coupling of a transmitting coil and a receiving coil occurs in awireless charging zone according to an example embodiment.

Referring to FIG. 5, in response to a coupling occurring between one ofthe transmitting coils 102, 103, 104, and 105 and the receiving coil 107located in the 3D wireless charging zone 106, a wireless chargingapparatus may form an induced current on the receiving coil 107. In thisexample, the wireless charging apparatus may form the quite zone in adirection the same as a direction of at least one receiving coil, thereceiving coil 107 located in the 3D wireless charging zone 106.

The wireless charging apparatus may determine a direction correspondingto a location of the receiving coil 107 in the 3D wireless charging zone106. The wireless charging apparatus may form a quite zone in adirection the same as the determined direction of the receiving coil107.

For example, the receiving coil 107 may be horizontally disposed in the3D wireless charging zone 106, and located adjacent to the transmittingcoil 104 among the transmitting coils 102, 103, 104, and 105. In thisexample, the wireless charging apparatus may horizontally form the quitezone using the transmitting coils 102 and 104. Since the receiving coil107 is located in a horizontal direction in the 3D wireless chargingzone 106, the receiving coil 107 may be connected to the transmittingcoils 102 and 104 forming a magnetic field in a horizontal axisdirection. The transmitting coils 102 and 104 may receive most of thecurrent from the power source 109.

Also, the induced current may be formed on the receiving coil 107through a resonance between the receiving coil 107 and the transmittingcoil 103 having a higher coupling coefficient between the transmittingcoils 102 and 104. For example, a magnetic field may be formed on thereceiving coil 107 by a quite zone formed on the transmitting coil 104,and an induced current may be formed based on the magnetic field.

FIG. 6 is a diagram illustrating a transmitting coil including acapacitor according to an example embodiment.

Referring to FIG. 6, a wireless charging apparatus may further includeat least one capacitor 601 configured to reduce sizes of thetransmitting coils 102, 103, 104, and 105 or reduce resonancefrequencies of the transmitting coils 102, 103, 104, and 105. The atleast one capacitor 601 may be located between at least one power sourceand the transmitting coils 102, 103, 104, and 105. The resonancefrequencies of the transmitting coils 102, 103, 104, and 105 connectedto the at least one capacitor 601 may be reduced by the at least onecapacitor 601.

For example, the transmitting coils 102, 103, 104, and 105 may form aquite zone based on a resonance frequency corresponding to a currentsupplied from a power source in general. In this example, the currentsupplied from the power source to the transmitting coils 102, 103, 104,and 105 connected to the at least one capacitor 601 may be filtered bythe at least one capacitor and thus, the resonance frequencycorresponding to the current may be reduced.

FIG. 7 is a diagram illustrating an operation of offsetting magneticfield formed on transmission coils arranged in a wireless charging zoneaccording to an example embodiment.

Referring to FIG. 7, the 3D wireless charging zone 106 may include anarea in which a transmission of a quite zone formed by the transmittingcoils 102, 103, 104, and 105 is unavailable. As illustrated in FIG. 7,when the receiving coil 107 is located at a corner of the 3D wirelesscharging zone 106, the quite zone formed by the transmitting coils 102,103, 104, and 105 may not be transmitted to the receiving coil 107.

The foregoing example may be based on a case in which an offset occursin a quite zone of at least one pair of transmitting coils. For example,a quite zone formed between the transmitting coils 102 and 104 and aquite zone formed between the transmitting coils 103 and 105 may beformed to cross each other and thus, an offset between the quite zonesmay occur. In this example, the area in which the transmission of thequite zone formed by the transmitting coils 102, 103, 104, and 105 isunavailable may be formed with respect to a predetermined area in the 3Dwireless charging zone 106.

In this disclosure, by controlling a phase of a current supplied from apower source, an environment may be constructed such that a wirelesscharging is performed in any location of the 3D wireless charging zone106 and an area in which a transmission of a quite zone is not formed.Related descriptions will be continuously provided with reference toFIGS. 8 through 10.

FIG. 8 is a graph illustrating a change in efficiency based on agradient between a receiving coil and a transmitting coil according toan example embodiment.

A graph of FIG. 8 represents a change in efficiency based on a gradientbetween a transmitting coil and a receiving coil 802. A wirelesscharging apparatus may operate in consideration of gradients betweentransmitting coils and the receiving coil located in a wireless chargingzone.

As shown in the graph of FIG. 8, when transmitting coils are arranged ona floor 801 of the 3D wireless charging zone 106, and when the receivingcoil 802 is disposed at an angle of θ, the wireless charging apparatusmay have a minimum efficiency of energy transmission in an area in whichthe angle of θ is 90°.

FIGS. 9A and 9B are diagrams illustrating a change in efficiency of theoffset magnetic field of FIG. 7 according to an example embodiment.

FIGS. 9A and 9B illustrate a case in which an energy efficiencydecreases due to an offset occurring in a magnetic field described withreference to FIG. 7. For example, an efficiency of receiving an energymay be obtained through a simulation performed by varying an angle of areceiving coil 905 in a wireless charging zone. As a result of thesimulation, as illustrated in FIGS. 9A and 9B, the receiving coil 905may have a null point at an angle of θ, for example, −45°.

A null point phenomenon may be a phenomenon appears commonly at cornersof a quadrangle structure and may occur due to an offset occurringbetween magnetic fields as described with reference to FIG. 7. In thisdisclosure, an issue of the offset occurring between the magnetic fieldsmay be solved by controlling a phase of a current supplied from a powersource.

FIG. 10 is a diagram illustrating current characteristics based on achange in phase of a current supplied from a power source according toan example embodiment.

FIG. 10 illustrates efficiency change characteristics associated with anull point typically occurring when a 90-degree out-of-phase current issupplied to the transmitting coils 901 and 902 as described withreference to FIG. 9.

In terms of the efficiency change characteristic that a null point valueis obtained at an angle of θ, for example, −45°, it is indicated that anefficiency of this system is improved when a phase of a current suppliedto the transmitting coils 901 and 902 is changed in comparison to aphase of a current supplied to the transmitting coils 903 and 904. Thus,an issue associated with a null point value obtained at a predeterminedlocation and a predetermined angle when an energy zone, that is, awireless charging zone is formed in a cubic structure may be solved bychanging a phase of a current supplied to a transmitting coil.

Accordingly, as described with reference to FIGS. 3A and 3B, adifference between a minimum current value and a maximum current valuemay be reduced when the transmitting coils 901 and 902 and thetransmitting coils 903 and 904 receive a 90-degree out-of-phase currentin comparison to the in-phase current and thus, a density of the quitezone formed in the 3D wireless charging zone may increase.

FIGS. 11A and 11B are diagrams illustrating an operation of controllinga phase of a magnetic field formed on transmission coils using aninverter included in a power source according to an example embodiment.

Referring to FIGS. 11A and 11B, a wireless charging apparatus may useone inverter, for example, an inverter 1101 to supply a current havingtwo phase signals to the transmitting coils 102, 103, 104, and 105.Also, the transmitting coils 103 and 105, and the transmitting coils 102and 104 may have different current phases based on the current suppliedfrom the inverter 1101.

For example, a current including two signals having different phases maybe generated in the inverter 1101. The current including the signalscorresponding to the two phases may be fed to the transmitting coils 103and 105 as an in-phase current. Also, with respect to the transmittingcoils 102 and 104, feeding may be performed at the same phase betweentransmitting coils implemented as two pairs with a current of a signalhaving the other phase. Here, as a method of feeding a current to atransmitting coil, a direct feeding method may be used to directly feeda current to a transmitting coil and an indirect feeding method may alsobe used to feed a current to a transmitting coil. To perform the method,a feeding coil may be additionally provided in a structure. Also, anin-phase current or an out-of-phase current may be fed to a pair oftransmitting coils and another pair of transmitting coils.

In this example, a location and an angle of the receiving coil 107 atwhich the null point occurs in the 3D wireless charging zone 106 may beverified. Also, in consideration of a point in time at which the nullpoint occurs, the inverter 1101 may generate an in-phase current andfeed the in-phase current to the transmitting coils 102, 103, 104, and105.

Also, in response to the feeding the in-phase current to thetransmitting coils 102, 103, 104, and 105, the point in time at whichthe null point occurs may disappear. That is, when the magnetic field istransferred to the point in time at which the null point occurs, thepoint in time at which the null point occurs may disappear.

In a case in which at least two receiving coils are provided, the numberof transmitting coils may increase. In such case, by much denselydefining the magnetic field formed on the transmitting coils 102, 103,104, and 105, the issue of the null point occurring in a plurality ofreceiving coils may be solved.

The issue of the null point occurring in a plurality of receiving coilsmay also be solved using a method to power on/off through a timedivision of a resonance period formed in a receiving coil.

FIGS. 12A through 12E are diagrams illustrating results of evaluation onan efficiency of a wireless charging apparatus using a 3D wirelesscharging zone according to an example embodiment.

FIGS. 12A through 12E illustrate results of evaluation on aneffectiveness of a wireless charging apparatus using a 3D wirelesscharging zone. Specifically, an actual prototype product associated witha wireless charging zone having a cubic structure of 30×30×30 cm³ may bemanufactured to evaluate an effectiveness of the foregoing examples. Atransmitting module manufactured for the evaluation may be an inverterformed in a switch amplifier structure to operate at a band of 300kilohertz (kHz), and two inverters having a difference in phase may beused in the prototype product. A receiver may be configured as a fullbridge-type rectifier circuit.

To evaluate an actual system, the evaluation may be performed through ameasurement based on a direct current (DC)-to-DC efficiency.Transmitting coils may be arranged in various locations, for example, amiddle left area, a middle area, a middle right area, a front part of afloor, and a middle part of the floor in the wireless charging zone, andthe measurement may be performed based on a corresponding location. Ineach of the locations, the measurement may be performed by rotating thereceiving coil by 0°, 45°, 90°, and 135°.

Also, the measurement may be performed by transitioning the inverter by0°, 90°, and 180° at each rotational angle and each of the locations. Asillustrated in FIGS. 12A through 12E, when one location and onerotational angle of the inverter is changed by 0°, 90°, and 180°, anoptimal efficiency may be achieved and an issue that an efficiencydecreases may be solved.

FIGS. 13A and 13B are diagrams illustrating a comparison between quitezones formed on transmitting coils arranged in a 3D wireless chargingzone according to an example embodiment.

Referring to FIGS. 13A and 13B, a simulation may be performed on anoperation of forming a quite zone having an equalized energy density ina wireless charging zone. In this example, to perform the simulation, anenvironment may be constructed to have a condition as further discussedbelow. For example, a cubic wireless charging zone may be formed. Also,transmitting coils may be arranged on four walls configuring the cubicwireless charging zone. The transmitting coils may be implemented as atleast one pair of transmitting coils arranged to each other based onlocations of the four walls. In an example of FIGS. 13A and 13B, atransmitting coil 1 and a transmitting coil 2 may be provided as a pair,and a transmitting coil 3 and a transmitting coil 4 may be provided as apair.

An in-phase current may be supplied to the pair of transmitting coils 1and 2 facing each other, and the in-phase current or a 90-degreeout-of-phase current may be supplied to the pair of transmitting coils 3and 4 facing each other. In this example, quite zones may be formed inthe wireless charging zone and sizes of the quite zones may be compared.

In this disclosure, a simulation environment may be constructed suchthat the 1 ampere (A) current is applied from a porter to the pair ofthe transmitting coils 1 and 2 and the pair of the transmitting coils 3and 4 through both in-phase feeding and 90°-phase-transitioned feeing.Also, a distribution of the quite zone obtained in the examples of FIGS.13A and 14A to correspond to the pair of the transmitting coils 1 and 2and the pair of the transmitting coils 3 and 4 receiving the 1 A currentbased on the simulation environment may be provided.

FIG. 13A illustrates a distribution of the quiet zones formed in thewireless charging zone in response to a 1 A current being applied to thetwo pairs of transmitting coils facing each other, for example, the pairof the transmitting coils 1 and 2 and the pair of the transmitting coils3 and 4, through an in-phase feeding.

In an example of FIG. 13A, a 1 A in-phase current may be applied to thetransmitting coils 1 and 2 and the transmitting coils 3 and 4. When aphase of a current set in a power source is zero degrees, a currenthaving the same phase corresponding to zero degrees may be supplied tothe transmitting coils 1 and 2 and the transmitting coils 3 and 4. Thus,the current may be supplied to the transmitting coils 1 and 2 and thetransmitting coils 3 and 4 through the in-phase feeding.

The transmitting coils 1 through 4 may form quite zones in the wirelesscharging to zone based on the in-phase current. In the wireless chargingzone, the quite zones may be provided in a form curved at apredetermined angle based on a phase of the in-phase current.

FIG. 13B illustrates a distribution of the quiet zones formed in thewireless charging zone in response to a 1 A current being applied to thetwo pairs of transmitting coils facing each other, for example, the pairof the transmitting coils 1 and 2 and the pair of the transmitting coils3 and 4, through a 90-degree out-of-phase feeding.

In an example of FIG. 13B, a 1 A out-of-phase current may be applied tothe transmitting coils 1 and 2 and the transmitting coils 3 and 4. Inthis example, a phase of the current supplied to the transmitting coils1 and 2 may be controlled to be zero degrees and a phase of the currentsupplied to the transmitting coils 3 and 4 may be controlled to be 90degrees. Also, the transmitting coils 1 and 2 and the transmitting coils3 and 4 having a difference in phase corresponding to 90 degrees mayform the quite zone having an equalized energy density in the wirelesscharging zone.

Accordingly, a difference between a minimum current value and a maximumcurrent value may be reduced when the transmitting coils 1 and 2 and thetransmitting coils 3 and 4 receive a 90-degree out-of-phase current incomparison to the in-phase current and thus, a density of the quite zoneformed in the 3D wireless charging zone may increase.

In a result of simulations of FIGS. 13A through 14, the quite zone ofthe pair of the transmitting coils 1 and 2 and the pair of thetransmitting coils 3 and 4 on which the in-phase feeding is performedmay be distributed in a range between 0.000269 and 6.109 amperes permeter (A/m) in the wireless charging zone. Also, the quite zone of thepair of the transmitting coils 1 and 2 and the pair of the transmittingcoils 3 and 4 on which the 90-degree out-of-phase feeding is performedmay be distributed in a range between 0.64 and 4.52 A/m in the wirelesscharging zone.

Accordingly, in terms of transmitting coils arranged in a wirelesscharging zone, when a difference in phase between two pairs oftransmitting coils, for example, the pair of the transmitting coils 1and 2 and the pair of the transmitting coils 3 and 4 is 90 degrees, aquite zone having an optimal charging effectiveness may be formed incomparison to a case in which the in-phase feeding is performed. When aphase of a current supplied to different transmitting coils paired witheach other is transitioned by 90 degrees, a magnetic field formed on thetransmitting coils may be equalized.

Forming of a denser quite zone in a wireless charging zone may indicateforming of a charging zone in which a predetermined induced current maybe generated irrespective of a direction and a location of a receivingcoil in the wireless charging zone.

FIG. 15 is a flowchart illustrating an operation performed by aprocessor of a wireless charging apparatus according to an exampleembodiment.

In operation 1501, a wireless charging apparatus may detect whether areceiving coil is present in a wireless charging zone in a state inwhich a plurality of transmitting coils and power sources are arrangedin the wireless charging zone. In this example, the wireless chargingapparatus may be maintained in an initial standby state and may performa charging operation when the receiving coil is present in the wirelesscharging zone.

In operation 1502, when the receiving coil is detected in the wirelesscharging zone, the wireless charging apparatus may supply currents setin the power sources to the plurality of transmitting coils and form aquite zone in the wireless charging zone. For example, the wirelesscharging apparatus may switch a state of an inverter maintained in theinitial standby state to supply the currents to the plurality oftransmitting coils. In this example, the inverter may supply the currentset to have the same phase or different phases to the plurality oftransmitting coils. When the inverter operates in the initial standbystate, the inverter may operate in a feeding mode at the same phase.

In operation 1503, the wireless charging apparatus may supply currentsincluding two signals having the same phase to the plurality oftransmitting coils.

In operation 1505, the wireless charging apparatus may detect a value ofan induced to current formed on the receiving coil using the currentsupplied to the plurality of transmitting coils.

When the detected value of the induced current is relatively small, thewireless charging apparatus may switch the state of the inverter inresponse to a feedback so as to perform feeding by changing a phase to areversed phase of the inverter. For example, the wireless chargingapparatus may change a phase of a current supplied to the plurality oftransmitting coils based on the value of the induced current formed on areceiving coil. The wireless charging apparatus 101 may change a phaseof a current set with respect to a current generated in a power sourceto a phase of a current based on an induced current. When currents setto have different phases are supplied, in operation 1504, the wirelesscharging apparatus may supply the current including the two signalshaving the different phases to the plurality of transmitting coils.

Thereafter, the wireless charging apparatus may redetect an inducedcurrent induced by a quite zone formed on the transmitting coils basedon the currents of which the phases are changed.

When a value of the detected induced current is normal, in operation1506, the wireless charging apparatus may maintain an inverter phasestate without change.

In operation 1507, the wireless charging apparatus may transmit energyto the receiving coil based on the phase of current supplied from theinverter in state of the inverter in the maintained phase. Through this,the wireless charging apparatus may complete charging of the receivingcoil.

In the present disclosure, there is provided an environment allowing thewireless charging apparatus to consistently verify received power or aninduced current with respect to a receiving coil disposed atpredetermined space, location, and location angle in a process of 3Dspace wireless charging such that the receiving coil consistentlyreceives energy in a normal state.

According to an aspect, it is possible to perform a wireless charging ofa battery in an electronic device using a receiving coil included in allelectronic device, for example, a wearable device and an IoT device tobe located in a wireless charging device based on a 3D wireless chargingstate in which a plurality of transmitting coils are arranged.

According to another aspect, it is possible to provide a wirelesscharging apparatus for performing a wireless charging withoutrestrictions on location in a wireless charging zone by controlling aphase of a current supplied to a transmitting coil based on a directionand a gradient of a receiving coil included in the wireless chargingzone.

The components described in the exemplary embodiments of the presentinvention may be achieved by hardware components including at least oneDSP (Digital Signal Processor), a processor, a controller, an ASIC(Application Specific Integrated Circuit), a programmable logic elementsuch as an FPGA (Field Programmable Gate Array), other electronicdevices, and combinations thereof. At least some of the functions or theprocesses described in the exemplary embodiments of the presentinvention may be achieved by software, and the software may be recordedon a recording medium. The components, the functions, and the processesdescribed in the exemplary embodiments of the present invention may beachieved by a combination of hardware and software.

The processing device described herein may be implemented using hardwarecomponents, software components, and/or a combination thereof. Forexample, the processing device and the component described herein may beimplemented using one or more general-purpose or special purposecomputers, such as, for example, a processor, a controller and anarithmetic logic unit (ALU), a digital signal processor, amicrocomputer, a field programmable gate array (FPGA), a programmablelogic unit (PLU), a microprocessor, or any other device capable ofresponding to and executing instructions in a defined manner. Theprocessing device may run an operating system (OS) and one or moresoftware applications that run on the OS. The processing device also mayaccess, store, manipulate, process, and create data in response toexecution of the software. For purpose of simplicity, the description ofa processing device is used as singular, however, one skilled in the artwill be appreciated that a processing device may include multipleprocessing elements and/or multiple types of processing elements. Forexample, a processing device may include multiple processors or aprocessor and a controller. In addition, different processingconfigurations are possible, such as parallel processors.

The methods according to the above-described example embodiments may berecorded in non-transitory computer-readable media including programinstructions to implement various operations of the above-describedexample embodiments. The media may also include, alone or in combinationwith the program instructions, data files, data structures, and thelike. The program instructions recorded on the media may be thosespecially designed and constructed for the purposes of exampleembodiments, or they may be of the kind well-known and available tothose having skill in the computer software arts. Examples ofnon-transitory computer-readable media include magnetic media such ashard disks, floppy disks, and magnetic tape; optical media such asCD-ROM discs, DVDs, and/or Blue-ray discs; magneto-optical media such asoptical discs; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory (ROM),random access memory (RAM), flash memory (e.g., USB flash drives, memorycards, memory sticks, etc.), and the like. Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter. The above-described devices may beconfigured to act as one or more software modules in order to performthe operations of the above-described example embodiments, or viceversa.

A number of example embodiments have been described above. Nevertheless,it should be understood that various modifications may be made to theseexample embodiments. For example, suitable results may be achieved ifthe described techniques are performed in a different order and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents. Accordingly, other implementations arewithin the scope of the following claims.

What is claimed is:
 1. A wireless charging apparatus comprising: aplurality of transmitting coils included in a wireless charging zone ina three-dimensional (3D) form; and at least one power source configuredto supply a current to the plurality of transmitting coils, wherein theat least one pair of transmitting coils are configured to form a quietzone indicating a magnetic field having an equalized energy density inthe wireless charging zone.
 2. The wireless charging apparatus of claim1, wherein the plurality of transmitting coils includes at least onepair of transmitting coils arranged to face each other in the wirelesscharging zone.
 3. The wireless charging apparatus of claim 2, a firstpair of transmitting coils arranged to face each in the wirelesscharging zone is configured to supply current having first phase, asecond pair of transmitting coils arranged to face each in the wirelesscharging zone is configured to supply current having second phase. 4.The wireless charging apparatus of claim 3, wherein the first phasediffers by 90 degrees from the second phase.
 5. The wireless chargingapparatus of claim 1, wherein the at least one power source includes: aninverter configured to control a phase of the current supplied to theplurality of transmitting coils.
 6. A wireless charging apparatuscomprising: a first pair of transmitting coils arranged to face eachother in a wireless charging zone in a three-dimensional (3D) form; asecond pair of transmitting coils arranged to face each other in awireless charging zone in a three-dimensional (3D) form; a power sourceconfigured to control a phase of a current supplied to the first pairand the second pair for forming a quiet zone indicating a magnetic fieldhaving an equalized energy density in the wireless charging zone.
 7. Thewireless charging apparatus of claim 6, a first pair of transmittingcoils arranged to face each in the wireless charging zone is configuredto supply current having first phase, a second pair of transmittingcoils arranged to face each in the wireless charging zone is configuredto supply current having second phase.
 8. The wireless chargingapparatus of claim 7, wherein the first phase differs by 90 degrees fromthe second phase.
 9. The wireless charging apparatus of claim 6, whereinthe at least one power source includes: an inverter configured tocontrol a phase of the current supplied to the plurality of transmittingcoils.
 10. A wireless charging apparatus comprising: a plurality oftransmitting coils arranged at a wireless charging zone; a power sourceconfigured to control a phase of a current supplied to the plurality oftransmitting coils for forming a quiet zone indicating a magnetic fieldhaving an equalized energy density in the wireless charging zone. 11.The wireless charging apparatus of claim 10, wherein the plurality oftransmitting coils is arranged to face each other.
 12. The wirelesscharging apparatus of claim 10, wherein the plurality of transmittingcoils are configured as pair, to wherein the power source suppliescurrent having same phase into transmitting coils in the same pair,wherein the power source supplies current having different phase intotransmitting coils in the different pair.